SYSTEM FOR CONTROLLING POWER DELIVERED TO ELECTRICAL LOAD

FIELD OF INVENTION

[0001] The invention generally relates to electrical appliances and more particularly to load control devices for controlling the amount of power delivered to an electrical load.

BACKGROUND OF THE INVENTION

[0002] Regulators described in the prior art for controlling operation of an electrical device such as speed of a fan and intensity of a lighting device comprise a potentiometer which is typically operated mechanically to control the resistance of the powering circuit and  hence  the speed of a fan (or brightness of a light).

[0003] One disadvantage associated with such regulators is inability of the regulators to be operated digitally. Further  absence of mechanism to interface the typical regulator with a home automation system is a limitation. This poses a hurdle in providing seamless control over various electrical devices using the home automation system. Therefore  the user experiences inconvenience while operating the regulator separately due to its inability to be integrated with the home automation system.

[0004] Hence there exists a need for a switching unit that provides ease of operation while exhibiting the ability to be integrated with the home automation system thereby enhancing the user experience while operating the electrical device.

BRIEF DESCRIPTION OF THE INVENTION

[0005] The above-mentioned shortcomings  disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification.

[0006] In one embodiment  a system for controlling power delivered to an electrical load is provided. The system comprises a variable voltage power source  a light emitting diode coupled to the variable voltage power source  the light emitting diode having multiple outputs representative of the varied brightness of the light emitting diode  a light dependent resistor coupled to the light emitting diode  the resistance of the light dependent resistor being controlled by the varied brightness of the light emitting diode and a bidirectional semiconductor switch coupled to the light dependent resistor and the electrical load  for conducting a load current from the variable voltage power source to the electrical load  the bidirectional semiconductor switch having a control input coupled to the light dependent resistor for operating the bidirectional semiconductor switch. Further  the variable voltage power source is coupled to the light emitting diode through one of a resistor banking unit and a frequency modulation unit.

[0007] In another embodiment  a system for controlling power delivered to an electrical load is provided. The system comprises a variable voltage power source  a potentiometer coupled to the variable voltage power source  a light emitting diode coupled to the variable voltage power source  the light emitting diode having multiple outputs representative of the varied brightness of the light emitting diode  a light dependent resistor coupled to the light emitting diode  the resistance of the light dependent resistor being controlled by the varied brightness of the light emitting diode  a control circuit coupled to the potentiometer  the control circuit configured for controlling the resistance of the system based on multiple control inputs and a bidirectional semiconductor switch coupled to the light dependent resistor and the electrical load  for conducting a load current from the variable voltage power source to the electrical load. The control circuit comprises one of a resistor banking unit and a frequency modulation unit for controlling the brightness of the light emitting diode.

[0008] Systems and methods of varying scope are described herein. In addition to the aspects and advantages described in this summary  further aspects and advantages will become apparent by reference to the drawings and with reference to the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 shows a block diagram of a system for controlling power delivered to an electrical load as described in one embodiment; and

[0010] FIG. 2 shows an exemplary schematic diagram of the system shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0011] In the following detailed description  reference is made to the accompanying drawings that form a part hereof  and in which is shown by way of illustration specific embodiments  which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments  and it is to be understood that other embodiments may be utilized and that logical  mechanical  electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is  therefore  not to be taken in a limiting sense.

[0012] The objective of the invention is to provide a digital dimmer circuit  which can be operated by controlled outputs. In order to control operation of an electrical load or appliance in a stepwise manner the digital dimmer circuits operate on the principle of controlling power delivered to the load. The same principle is employed in the invention to convert a conventional regulator type switching device so as to configure it to a switching means which can control the operation of the electrical appliance digitally.

[0013] The digital dimmer circuits can be employed as switching means to control the operation of various electrical devices such as a light  a heater  an air conditioning unit  a music player  a fan and opening and closing of a curtain for example. The digital dimmer circuits employ phase control in the sense a controlled input is received at one of the inputs. The controlled input controls the point on the AC supply voltage at which the input is supplied to the electrical load. A point on the supply voltage waveform subsequent to the zero crossing is used to provide the controlled input to the electrical device such that the total energy delivered as input to the electrical device is reduced. The period between zero crossing and switching is controlled by an external control interface  which is typically a 0-10V DC control voltage  or a digital DMX512 interface. The external control interface can control loads of up to 2A (460VA).

[0014] FIG. 1 shows a block diagram of a system 100 for controlling power delivered to an electrical load. The system 100 comprises a variable voltage power source 105  a light emitting diode 110 (LED 110) coupled to the variable voltage power source 105  the light emitting diode 110 having multiple outputs representative of the varied brightness of the light emitting diode 110 and a light dependent resistor 115 (LDR 115) coupled to the light emitting diode 110  the resistance of the light dependent resistor 115 being controlled by the varied brightness of the light emitting diode 110.

[0015] The system 100 for controlling power delivered to the electrical appliance as described herein can be used in conjunction with conventional regulator type switching devices so as to configure the conventional regulators to function as digital regulators. The system 100 comprises the LDR 115 in series with the conventional regulator type switching device.

[0016] Since the light incident on the LDR 115 controls the power delivered to the electrical appliance  in order to enhance the accuracy of the system 100  it is desirable to insulate the LDR 115 from receiving light from other sources.

[0017] FIG. 2 shows a schematic diagram of the system 100 shown in FIG. 1. The system 100 does not dictate that the LDR 115 used is to be of particular specification and therefore can work with any of the readily available LDRs. The characteristics of the system 100 provided herein vary depending mainly on the LED 110 and LDR 115 characteristics.

[0018] The control voltage supplied to the electrical load is optically isolated from the system 100 connected to main power supply. In order to ensure a desired degree of electrical isolation  sufficient physical separation between the LED 110 and the LDR 115 is provided. An alternate means to provide electrical isolation is to employ a transparent isolator between the LED 110 and the LDR 115. The control voltage can further be controlled with a potentiometer connected in series with the LED 110. The potentiometer adds another dimension to the resistance of the circuit. The overall resistance of the system 100 is dependent on the potentiometer settings and on the intensity of light incident on the LDR 115. The resistance range of the potentiometer is varied based on the applications such that the resistance of the potentiometer is dependent on the sensitive range of resistance desired by the application.

[0019] In one embodiment  the brightness of the LED 110 can be controlled using a control circuit. The control circuit comprises one of a resistor banking circuit and a frequency modulation circuit. To control the brightness of the light incident on the LDR 115  the LED 110 is coupled to the resistor banking unit with three inputs (to be regulated by the user). The LED 110 is connected to a variable voltage power source 105 with three different inputs coupled to output of a regulator controlled by the user. The resistors in the resistor banking unit work on active low signals (which is ground when active and exhibit high impedance when not switched on). The value of each resistor in the resistor banking unit vary and therefore the brightness of the LED 110 varies. Each input has a different value of resistance and hence gives a different brightness in the LED 110 when connected. This effectively controls the resistance of LDR 115 and eventually the power delivered to the electrical appliance. The power delivered to the electrical appliance increases as the resistance of the LDR 115 decreases.

[0020] In another embodiment  the brightness of the LED 110 is controlled by the frequency modulation circuit. The frequency modulation circuit comprises a frequency synthesizer circuit. The output from the regulator is coupled to the input of the frequency synthesizer so as to generate a signal having a frequency representative of the input given by the user. The signal thus generated controls the brightness of LED 110 and in turn resistance of LDR 115 and eventually the power delivered to the electrical appliance.

[0021] Skilled artisans shall however appreciate that the LED 110 and LDR 115 combination can be replaced by a phototransistor  an optocoupler or a similar device.

[0022] The bidirectional semiconductor switch 120 is coupled to the light dependent resistor 115 and the electrical load  for conducting the load current from the variable voltage power source 105 to the electrical load. The bidirectional semiconductor switch 120 has a control input coupled to the light dependent resistor 115 for operating the bidirectional semiconductor switch 120. The bidirectional semiconductor switch 120 comprises at least one of a DIAC (Diode for Alternating Current)  TRIAC (Triode for Alternating Current) based switching system 100 and SCR (Silicon Controlled Rectifier) based switching system 100.

[0023] In various embodiments of the invention  a system for controlling power delivered to an electrical device is described. However  the embodiments are not limited and may be implemented in connection with different applications. The application of the invention can be extended to other areas  for example electronic devices. The invention provides a broad concept of using a photo sensitive device to control power delivered to an electrical appliance  which can be adapted in a similar powering system. The design can be carried further and implemented in various forms and specifications.

[0024] This written description uses examples to describe the subject matter herein  including the best mode  and also to enable any person skilled in the art to make and use the subject matter. The patentable scope of the subject matter is defined by the claims  and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims  or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

CLAIMS

What is claimed is:
1. A system for controlling power delivered to an electrical load  the system comprising:
a variable voltage power source;
a light emitting diode coupled to the variable voltage power source  the light emitting diode having multiple outputs representative of the varied brightness of the light emitting diode;
a light dependent resistor coupled to the light emitting diode  the resistance of the light dependent resistor being controlled by the varied brightness of the light emitting diode; and
a bidirectional semiconductor switch coupled to the light dependent resistor and the electrical load  for conducting a load current from the variable voltage power source to the electrical load  the bidirectional semiconductor switch having a control input coupled to the light dependent resistor for operating the bidirectional semiconductor switch;
wherein the variable voltage power source is coupled to the light emitting diode through one of a resistor banking unit and a frequency modulation unit.

2. The system of claim 1  further comprising a potentiometer coupled in series with the light dependent resistor.

3. The system of claim 1  wherein the intensity of the light emitting diode is controlled by the frequency modulation unit.

4. The system of claim 1  wherein multiple outputs of the light emitting diode are coupled to the resistor banking unit having multiple inputs.

5. The system of claim 1  wherein each of the multiple outputs of the light emitting diode are configured to operate on active low signals.

6. A system for controlling power delivered to an electrical load  the system comprising:
a variable voltage power source;
a light emitting diode coupled to the variable voltage power source  the light emitting diode having multiple outputs representative of the varied brightness of the light emitting diode;
a light dependent resistor coupled to the light emitting diode  the resistance of the light dependent resistor being controlled by the varied brightness of the light emitting diode;
a potentiometer coupled to the light emitting diode;
a control circuit coupled to the variable voltage power source and the light emitting diode  the control circuit configured for controlling the resistance of the system based on multiple control inputs; a bidirectional semiconductor switch coupled to the light dependent resistor and the electrical load  for conducting a load current from the variable voltage power source to the electrical load;
wherein the control circuit comprises one of a resistor banking unit and a frequency modulation unit for controlling the brightness of the light emitting diode.

7. The system of claim 6  wherein the brightness of the light emitting diode is controlled by the frequency modulation unit.

8. The system of claim 6  wherein multiple outputs of the light emitting diode are coupled to the resistor banking unit having multiple inputs.

9. The system of claim 6  wherein each of the resistors in the resistor banking unit has a different resistance value.
10. The system of claim 6  wherein each of the multiple outputs of the light emitting diode are configured to operate on active low signals.